1. Field of the Invention
The present invention relates generally to treatment of target disease areas of the body, including inner ear disorders, such as Meniere's disease, tinnitus, and hearing loss. More particularly, the present invention relates to a method and apparatus for administering medication to the disease target area, such as the middle ear and/or inner ear (or cochlea).
2. Related Art
Various situations or medical conditions of the inner ear require the administration of drugs or like medicines to the middle ear. Such medical conditions or inner ear disorders can include sudden neurosensory hearing loss, Meniere's disease, and tinnitus. These conditions affect up to 40 million persons in the United States, and are the cause of significant loss of productivity and quality of life. Costs to the U.S. military related to treatment of sudden neurosensory hearing loss are estimated at 1.5 billion dollars per year.
For example, Meniere's disease, also known as idiopathic endolymphatic hydrops, is classified as an inner ear disorder. Meniere's disease is characterized by episodic rotational vertigo (spinning sensation or dizziness), hearing loss, tinnitus (ringing, buzzing or roaring in the ears), and a sensation of pressure or fullness in the ear. The vertigo of Meniere's disease occurs in attacks of a spinning sensation, and is accompanied by dysequilibrium (an off-balance sensation), nausea, and vomiting. The vertigo lasts from 20 minutes to 2 hours (or more), during which the person is unable to perform normal activities.
Sudden neurosensory hearing loss, Meniere's disease, and tinnitus usually may be treated medically or surgically. Various medications may be taken in conjunction with a low salt diet. Such medications include urea, glycerol, isosorbide, diuretics (dyazide), acetazolamide (Diamox), steroids (prednisone or dexamethasone), antibiotics (gentamycin), calcium channel blockers (Fluanarizine or Cinnarzine), niacin, betahistine (Serc), or anesthetics.
One disadvantage with medications is that they are often administered orally or intravenously, each of which results in a systemic administration of the medication. Systemic administration of medication is problematic in some applications in that the medication is distributed throughout much of the patient's body. By distributing the medication throughout the patient's body, concentrations of the medication vary in different parts of the body. For instance, the concentration of the medication may be low in one area of the body but relatively high in other areas.
It is generally advantageous to treat a diseased portion of the body with a therapeutic concentration of the medication being administered, that is, a concentration high enough to effectively treat the condition but not so high as to reach a toxic level. However, it is often the case that systemic administration of medication is problematic in that the desired therapeutic level of medication is delivered to the diseased portion of the body that is being treated, but higher than therapeutic levels are delivered to other parts of the body. This can lead to the serious and undesirable result of systemic toxicity.
Surgical procedures used to treat these conditions include endolymphatic shunt, insertion of a Tympanostomy tube, sacculotomy, cochleosacculotomy, endolymphatic sac surgery, chemical labyrinthectomy with antibiotics, surgical labyrinthectomy, and vestibular nerve section surgery. The endolymphatic shunt procedure drains excess fluids from the inner ear. An incision is made behind the ear, through the mastoid, and a tube is inserted.
Insertion of a Tympanostomy tube is a minor procedure in which a tiny tube is inserted and maintained in a hole through the eardrum. Sacculotomy and cochleosacculotomy are also relatively minor procedures which involve perforation of the saccule through the stapes footplate (sacculotomy), or through the round window, via the basilar membrane (cochleosacculotomy).
Endolymphatic sac surgery includes: endolymphatic sac decompression, in which bone overlying the endolymphatic sac is drilled away to make a larger cavity for the sac; endolymph-subarachnoid shunt, which involves placing a tube between the endolymphatic sac and the cranium; endolymph-mastoid shunt, which involves placing a tube between the endolymphatic sac and the mastoid cavity; and endolymphatic sac ablation, which completely destroys the endolymphatic sac.
Chemical labyrinthectomy destroys the vestibular system, or vestibular hair cells, using certain antibiotics. Surgical labyrinthectomy is the surgical destruction of either a portion or the entire labyrinth. Finally, vestibular nerve section surgery cuts the nerve from the vestibular apparatus.
One disadvantage with surgical treatment is the expense and invasiveness of surgery. In addition, many of the surgical procedures used for treating these disorders are considered controversial.